There are 4 equally sized glasses with the same amount of water in them. 2 teaspoons of sand are poured into the first glass, two teaspoons of sugar into the second glass, two teaspoons of salt into the third glass and two teaspoons of flour into the 4th glass. Each mixture is stirred for the same amount of time.

Which 4 things in this investigation are the control?

The 4 things in this investigation that are the control are:

1. The equally sized glasses
2. The amount of water in each glass
3. The amount of time each mixture is stirred for
4. The fact that each mixture is stirred with the same intensity or force.